The aspherical reflector surface is tested based on basic phase measuring deflectometry, and the mid-high frequency error of result is studied. The intensity-modulated patterns are displayed on the thin film transistor screens. The camera observes and records the fringe pattern reflected by the tested reflector. The phase distribution is obtained by the phase-shifting and phase unwrapping technique. The surface normal is obtained through ray trace, the surface profile gradient distribution is obtained according to reflection law. And the surface is reconstructed by numerical integration. The mid-high frequency error is studied by the Zernike polynomial fitting.